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Cited by 106Phytoestrogen effects and researchNutritional Studies and DietCancer Risks and Factors

Soy food consumption and breast cancer prognosis

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Caan, Bette J., Natarajan, Loki, Parker, Barbara, Gold, Ellen B., Thomson, Cynthia, Newman, Vicky, Rock, Cheryl L., Pu, Minya, Al-Delaimy, Wael, Pierce, John P.·2011·Cancer Epidemiology, Biomarkers & Prevention
DOI 10.1158/1055-9965.epi-10-1041PMC PMC7359724
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Abstract

Background: Contrary to earlier clinical studies suggesting that soy may promote breast tumor growth, two recent studies show that soy-containing foods are not adversely related to breast cancer prognosis. We examined, using data from the Women's Healthy Eating and Living (WHEL) study, the effect of soy intake on breast cancer prognosis. Methods: Three thousand eighty-eight breast cancer survivors, diagnosed between 1991 and 2000 with early-stage breast cancer and participating in WHEL, were followed for a median of 7.3 years. Isoflavone intakes were measured postdiagnosis by using a food frequency questionnaire. Women self-reported new outcome events semiannually, which were then verified by medical records and/or death certificates. HRs and 95% CIs representing the association between either a second breast cancer event or death and soy intake were computed, adjusting for study group and other covariates, using the delayed entry Cox proportional hazards model. Results: As isoflavone intake increased, risk of death decreased (P for trend = 0.02). Women at the highest levels of isoflavone intake (>16.3 mg isoflavones) had a nonsignificant 54% reduction in risk of death. Conclusion: Our study is the third epidemiologic study to report no adverse effects of soy foods on breast cancer prognosis. Impact: These studies, taken together, which vary in ethnic composition (two from the United States and one from China) and by level and type of soy consumption, provide the necessary epidemiologic evidence that clinicians no longer need to advise against soy consumption for women with a diagnosis of breast cancer. Cancer Epidemiol Biomarkers Prev; 20(5); 854–8. ©2011 AACR.

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  • Of five prospective studies reporting on recurrence, two (40%) showed protective effects.

    “Of five studies reporting on recurrence [97,100,103,106,112], two (40%) showed protective effects [106,112].”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [100]

    The Results (page unavailable) say soy isoflavone intake was unrelated to the risk of a second breast cancer event and that no intake level showed a significant decrease in risk. The paper discusses a possible protective association with mortality, not recurrence, so it does not support counting this study among those showing a protective effect on recurrence. (LLM, conf=0.89)

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  • Caan et al reported a trend toward decreased risk of death among tamoxifen users with intake of total isoflavones ≥6.3mg per day (median 26.7mg), HR 0.26 (0.06-1.01, ptrend=0.05), and also among women with ER+ or PR+ status, HR 0.31 (0.10-0.98, ptrend=0.07), but this was not significant.

    “Caan et al reported a trend toward decreased risk of death among tamoxifen users with intake of total isoflavones ≥6.3mg per day (median 26.7mg), HR 0.26 (0.06-1.01, ptrend=0.05), and also among women with ER+ or PR+ status, HR 0.31 (0.10-0.98, ptrend=0.07), but this was not significant [100].”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [100]

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  • Of seven prospective studies examining survival, four (57%) showed protective effects on breast cancer mortality or mortality in breast cancer patients.

    “Of seven studies examining survival [94,96,98,100,101,106,112], four (57%) showed protective effects on breast cancer mortality or mortality in breast cancer patients [94,96,101,112].”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [100]

    The Results report a trend toward lower all-cause mortality with greater soy intake among breast cancer survivors (p for trend=0.02). But the reduction in the highest-intake group was not statistically significant, and the Discussion calls the association ‘suggested.’ This supports including the study as evidence of a possible protective association, but ‘showed protective effects’ overstates its finding. (LLM, conf=0.84)

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  • Four cohort studies and three RCTs reported no significant differences in treatment outcomes or rates of adverse effects associated with soy use among women receiving tamoxifen therapy.

    “Four cohort studies [100,103,106,112] and three RCTs [128,130,131] reported no significant differences with respect to treatment outcomes or rates of adverse effects associated with use of soy among women who were receiving tamoxifen therapy.”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [100]

    The Results report no significant association between soy intake and a second breast cancer event among women who had ever used tamoxifen; analyses restricted to current users did not change the results. But the paper also reports a trend toward lower mortality with greater soy intake among tamoxifen users (p for trend=0.05), and it does not report rates of treatment side effects. Its outcome findings therefore support only part of the attributed statement. (LLM, conf=0.85)

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  • The WHEL cohort had relatively low soy isoflavone intake (≥6.3 mg total isoflavones) and yielded null results, with an HR for recurrence among tamoxifen users of 0.59 (0.27-1.29).

    “Of the cohort studies, the WHEL cohort exhibited relatively low soy isoflavone intake (≥6.3mg total isoflavones) and yielded null results: HR for recurrence among tamoxifen users was 0.59 (0.27-1.29) [100].”

    From Soy, Red Clover, and Isoflavones and Breast Cancer: A Systematic Review (2013) · cites this paper as [100]

    The Discussion describes mean soy intake in WHEL as much lower than in a Chinese cohort, and Data Analyses identifies 6.3–86.9 mg/day as the highest intake category. The Results report no significant association with a second breast cancer event among women who had ever used tamoxifen. The exact HR of 0.59 and 95% CI of 0.27–1.29 are not stated in the available passages, so those figures cannot be verified from our copy. (LLM, conf=0.84)

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Cites

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Research works printed but not linked: 16

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Authors
Caan, B. J., Natarajan, L., Parker, B., Gold, E. B., Thomson, C., Newman, V., Rock, C. L., Pu, M., Al-Delaimy, W., & Pierce, J. P.
Affiliations
  • Kaiser Permanente (US)
  • Authors' Affiliations: 1Division of Research, Kaiser Permanente, Oakland; 2Moores Cancer Center, University of California, San Diego, La Jolla; 3Department of Public Health Sciences, UC Davis School of Medicine, Davis, California; and 4Department of Nutritional Sciences, Arizona Cancer Center, University of Arizona, Tuscon, Arizona
Corresponding author
Caan, Bette J.
ORCID
Venue
Cancer Epidemiology, Biomarkers & Prevention
Publisher
American Association for Cancer Research (AACR)
Published
2011-05-01
Volume
20
Issue
5
Pages
854-858
ISSN
  • 1055-9965 (ISSN-L)
  • 1538-7755
DOI
10.1158/1055-9965.epi-10-1041
PMC
PMC7359724
OpenAlex
W2147968542
Cited by
106
References
1
Citations by year
2026: 4 · 2025: 4 · 2024: 5 · 2023: 2 · 2022: 4 · 2021: 5 · 2020: 6 · 2019: 5 · 2018: 8 · 2017: 8 · 2016: 10 · 2015: 5 · 2014: 4 · 2013: 12 · 2012: 19
FWCI
8.27
Type
journal article
Language
en
Open access
Locations
  • Cancer Epidemiology Biomarkers & Prevention (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
Funders
National Cancer Institute (R01CA069375)
Topics
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Phytoestrogen effects and research
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Nutritional Studies and Diet
  • Health Sciences › Medicine › Oncology › Cancer Risks and Factors
Keywords
soy products, breast cancer prognosis, isoflavones, breast cancer survivors, breast cancer recurrence, mortality, dietary intake
MeSH terms
Adolescent, Adult, Aged, Breast Neoplasms, China, Female, Humans, Middle Aged, Neoplasm Invasiveness, Prognosis, Surveys and Questionnaires, United States, Case-Control Studies, Randomized Controlled Trials as Topic, Survivors, Soy Foods, Young Adult

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